A quote from Major Gen. Peter Pace:
The Taliban "may be a day-to-day tactical problem for us, but we are a long-term strategic problem for them. They can pick and choose some battles, but they cannot take over this country again."
In court, we ask for "the truth, the whole truth, and nothing but the truth". I would say that General Pace is guilty of not telling the whole truth. The whole truth would be "they cannot take over this country again, for as long as we decide to be here," because they know and we know that unless we boost our involvement in Afghanistan to unprecedented levels, once we leave the Taliban is going to make a strong bid to take over again.
I think it's true that they will never be at their previous level of strength again, largely because they lost most of they sympathy the general populace had for them. However, nature abhors a vacuum and Afghanis hate the warlords who ruled over them before, so there is still enough support for the Taliban, both from inside the country and out that they will be dangerous for a long time to come.
If you read what we've written about Afghanistan before, you must certainly realize that there is no victory in sight for coalition forces in Afghanistan.